Remarkable progress made in microelectronic devices over the past several years has led to more useful yet less expensive electronic products of all types. It has also led to entirely new types of products. A major factor in the development of microelectronic devices has been the machines and methods used to manufacture them. Manufacturing of microelectronic devices requires extreme precision, extremely pure materials, and an extremely clean manufacturing environment. Even microscopic particles can cause defects and failures in devices.
Microelectronic devices are typically manufactured on a front or device side of a semiconductor wafer. In general, no microelectronic devices are on the back side of the wafer. However, contaminants on the back side of the wafer, such as metal particles, residues, films, etc., if not removed, can result in damage to devices on the front side of the wafer. For example, certain metals used in the manufacturing process, such as copper, can migrate through the wafer, from the back side to the front side, where they can cause defects in the microelectronic devices. Processing the backside of the wafer is therefore important.
The back side of the wafer may be processed using existing techniques, to remove contaminants. These techniques involve applying process fluids onto the back side, usually while spinning the wafer. However, the process fluids may damage microelectronic devices if the process fluids contact the front side of the wafer. Therefore, during back side processing, or single side processing in general, the process fluids should ideally make minimal or no contact with the front side or opposite side of the wafer. As the process fluids include liquids, gases or vapors, and as the wafer is usually spinning when they are applied, this objective has largely not yet been reached with current wafer processing technology.
Wafer processing machines have used various designs to try to solve the problem of how to exclude process fluids from the front side while processing the back side. Some of these machines have used flows of inert gas to try to confine the process fluids only to the back side. Others have used gaskets, membranes, or other types of mechanical seals or barriers to keep the process fluids off of the top side of the wafer. However, in the machines using gas flow, some amounts of process fluids tend to still reach the front or device side of the wafer. In the machines using mechanical seals, the seal must physically touch the device side of the wafer. This physical touching may damage microelectronic devices. Consequently, use of seals or physical barriers can have serious disadvantages.
Physical contact with the wafer by seals, fingers, clamps or other sealing, holding or positioning elements, as often used in current processing machines, creates risk of contamination via particle generation or particle release. These types of elements can also disrupt the uniform flow of process fluids on the wafer, resulting in varying degrees of processing at different areas of the wafer. Accordingly, regardless of whether one side or both sides are processed, minimizing physical contact with wafer generally provides better results. On the other hand, the wafer must be properly positioned and secured in place during processing. Accordingly, better machines and methods are needed to provide single side wafer processing, and for processing generally with less physical contact with the wafer.